dmaengine: hsu: remove redundant pieces of code

There are few places where the implemented pieces of code are not needed, i.e.:
- direction can't be wrong in hsu_dma_chan_start()
- desc->active set to 0 by kzalloc
- DMAEngine is NULL-aware when call ->device_alloc_chan_resources()

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>